mirror of
https://github.com/uhi22/pyPLC.git
synced 2024-11-20 01:13:58 +00:00
added udp checksum
This commit is contained in:
uhi22
parent
16c30bd3b4
commit
a2577a70fd
2 changed files with 174 additions and 3 deletions
11
pyPlcIpv6.py
11
pyPlcIpv6.py
|
|
@ -17,6 +17,7 @@
|
|||
# on the 6 byte MAC address.
|
||||
|
||||
from helpers import showAsHex
|
||||
import udpChecksum
|
||||
|
||||
|
||||
class ipv6handler():
|
||||
|
|
@ -80,12 +81,16 @@ class ipv6handler():
|
|||
lenInclChecksum = len(buffer) + 8
|
||||
self.UdpResponse[4] = lenInclChecksum >> 8
|
||||
self.UdpResponse[5] = lenInclChecksum & 0xFF
|
||||
checksum = 0x1234 # todo: calculate this checksum, see https://en.wikipedia.org/wiki/User_Datagram_Protocol
|
||||
self.UdpResponse[6] = checksum >> 8
|
||||
self.UdpResponse[7] = checksum & 0xFF
|
||||
# checksum will be calculated afterwards
|
||||
self.UdpResponse[6] = 0
|
||||
self.UdpResponse[7] = 0
|
||||
for i in range(0, len(buffer)):
|
||||
self.UdpResponse[8+i] = buffer[i]
|
||||
showAsHex(self.UdpResponse, "UDP response ")
|
||||
# The content of buffer is ready. We can calculate the checksum. see https://en.wikipedia.org/wiki/User_Datagram_Protocol
|
||||
checksum = udpChecksum.calculateUdpChecksumForIPv6(self.UdpResponse, self.SeccIp, self.EvccIp)
|
||||
self.UdpResponse[6] = checksum >> 8
|
||||
self.UdpResponse[7] = checksum & 0xFF
|
||||
self.packResponseIntoIp(self.UdpResponse)
|
||||
|
||||
def sendSdpResponse(self):
|
||||
|
|
|
|||
166
udpChecksum.py
Normal file
166
udpChecksum.py
Normal file
|
|
@ -0,0 +1,166 @@
|
|||
|
||||
# Calculation for UDP checksum
|
||||
#
|
||||
# This module calculates the UDP checksum in case of IPv6 usage.
|
||||
#
|
||||
from helpers import showAsHex
|
||||
|
||||
# A valid ethernet frame, containing IPv6 and UDP, to verify the checksum algorithm.
|
||||
testethernetframe = [
|
||||
0x33 , 0x33 , 0x00 , 0x00 , 0x00 , 0x01,
|
||||
0x04 , 0x65 , 0x65 , 0x00 , 0x64 , 0xc3 ,
|
||||
0x86 , 0xdd ,
|
||||
0x60 , 0x00
|
||||
, 0x00 , 0x00 , 0x00 , 0x12 , 0x11 , 0x0a , 0xfe , 0x80 , 0x00 , 0x00 , 0x00 , 0x00 , 0x00 , 0x00 , 0x06 , 0x65
|
||||
, 0x65 , 0xff , 0xfe , 0x00 , 0x64 , 0xc3 , 0xff , 0x02 , 0x00 , 0x00 , 0x00 , 0x00 , 0x00 , 0x00 , 0x00 , 0x00
|
||||
, 0x00 , 0x00 , 0x00 , 0x00 , 0x00 , 0x01 , 0xcc , 0xaf , 0x3b , 0x0e , 0x00 , 0x12 , 0x89 , 0x5e , 0x01 , 0xfe
|
||||
, 0x90 , 0x00 , 0x00 , 0x00 , 0x00 , 0x02 , 0x10 , 0x00 ]
|
||||
|
||||
|
||||
|
||||
def calculateUdpChecksumForIPv6(udpframe, ipv6source, ipv6dest):
|
||||
# Parameters:
|
||||
# udpframe: the udp frame including udp header and udppayload
|
||||
# ipv6source: the 16 byte IPv6 source address. Must be the same, which is used later for the transmission.
|
||||
# ipv6source: the 16 byte IPv6 destination address. Must be the same, which is used later for the transmission.
|
||||
udpframe[6] = 0 # at the beginning, set the checksum in the udp header to 00 00.
|
||||
udpframe[7] = 0
|
||||
# construct an array, consisting of a 40-byte-pseudo-ipv6-header, and the udp frame (consisting of udp header and udppayload)
|
||||
bufferlen = 40+len(udpframe)
|
||||
if ((bufferlen & 1)!=0):
|
||||
# if we have an odd buffer length, we need to add a padding byte in the end, because the sum calculation
|
||||
# will need 16-bit-aligned data.
|
||||
bufferlen+=1
|
||||
buffer = bytearray(bufferlen)
|
||||
for i in range(0, len(buffer)):
|
||||
buffer[i] = 0 # everything 0 for clean initialization
|
||||
# fill the pseudo-ipv6-header
|
||||
for i in range(0, 16): # copy 16 bytes IPv6 addresses
|
||||
buffer[i] = ipv6source[i] # IPv6 source address
|
||||
buffer[16+i] = ipv6dest[i] # IPv6 destination address
|
||||
udplen = len(udpframe)
|
||||
nxt = 0x11 # should be 0x11 in case of udp
|
||||
buffer[32] = 0 # high byte of the FOUR byte length is always 0
|
||||
buffer[33] = 0 # 2nd byte of the FOUR byte length is always 0
|
||||
buffer[34] = udplen >> 8 # 3rd
|
||||
buffer[35] = udplen & 0xFF # low byte of the FOUR byte length
|
||||
buffer[36] = 0 # 3 padding bytes with 0x00
|
||||
buffer[37] = 0
|
||||
buffer[38] = 0
|
||||
buffer[39] = nxt # the nxt is at the end of the pseudo header
|
||||
# pseudo-ipv6-header finished. Now lets put the udpframe into the buffer. (Containing udp header and udppayload)
|
||||
for i in range(0, len(udpframe)):
|
||||
buffer[40+i] = udpframe[i]
|
||||
# showAsHex(buffer, "buffer ")
|
||||
# buffer is prepared. Run the checksum over the complete buffer.
|
||||
totalSum = 0
|
||||
for i in range(0, len(buffer)>>1): # running through the complete buffer, in 2-byte-steps
|
||||
value16 = buffer[2*i] * 256 + buffer[2*i+1] # take the current 16-bit-word
|
||||
totalSum += value16 # we start with a normal addition of the value to the totalSum
|
||||
# But we do not want normal addition, we want a 16 bit one's complement sum,
|
||||
# see https://en.wikipedia.org/wiki/User_Datagram_Protocol
|
||||
if (totalSum>=65536): # On each addition, if a carry-out (17th bit) is produced,
|
||||
totalSum-=65536 # swing that 17th carry bit around
|
||||
totalSum+=1 # and add it to the least significant bit of the running total.
|
||||
# Finally, the sum is then one's complemented to yield the value of the UDP checksum field.
|
||||
checksum = totalSum ^ 0xffff
|
||||
return checksum
|
||||
|
||||
|
||||
if __name__ == "__main__":
|
||||
print("Testing the udp checksum calculation...")
|
||||
showAsHex(testethernetframe, "testethernetframe ")
|
||||
ipv6frame = bytearray(len(testethernetframe)-6-6-2) # without the ethernet header (MAC, MAC, ethertype)
|
||||
for i in range(0, len(ipv6frame)):
|
||||
ipv6frame[i] = testethernetframe[14+i]
|
||||
|
||||
showAsHex(ipv6frame, "ipv6frame ")
|
||||
# checksum calculation see https://en.wikipedia.org/wiki/User_Datagram_Protocol
|
||||
|
||||
# We want to calculate the UDP checksum. This needs to include also some data from "lower level" IP header, so we need the complete IP frame, not
|
||||
# only the UDP part.
|
||||
#
|
||||
# From wikipedia.org: Checksum is the 16-bit one's complement
|
||||
# of the one's complement sum of a pseudo header of information from
|
||||
# * the IP header,
|
||||
# * the UDP header,
|
||||
# * and the data,
|
||||
# padded with zero octets at the end (if necessary) to make a multiple of two octets.
|
||||
|
||||
# The pseudoIPv6 header for checksum calculation has a DIFFERENT format then a normal IPv6 header. So we cannot use the original frame,
|
||||
# instead, we copy the relevant information out of it into a dedicated buffer.
|
||||
# We have IPv6, so the IP header is
|
||||
ipv6pseudoheader = bytearray(40)
|
||||
for i in range(0, 16):
|
||||
ipv6pseudoheader[i] = ipv6frame[8+i] # IPv6 source address
|
||||
ipv6pseudoheader[16+i] = ipv6frame[24+i] # IPv6 destination address
|
||||
udplen = ipv6frame[4]*256 + ipv6frame[5] # the real IPv6 header has a two byte length info
|
||||
nxt = ipv6frame[6] # the real IPv6 header next-protocol information (should be 0x11 in case of udp)
|
||||
print("udplen=" + str(udplen))
|
||||
print("nxt=" + str(nxt))
|
||||
ipv6pseudoheader[32] = 0 # high byte of the FOUR byte length is always 0
|
||||
ipv6pseudoheader[33] = 0 # 2nd byte of the FOUR byte length is always 0
|
||||
ipv6pseudoheader[34] = udplen >> 8 # 3rd
|
||||
ipv6pseudoheader[35] = udplen & 0xFF # low byte of the FOUR byte length
|
||||
ipv6pseudoheader[36] = 0 # 3 padding bytes with 0x00
|
||||
ipv6pseudoheader[37] = 0
|
||||
ipv6pseudoheader[38] = 0
|
||||
ipv6pseudoheader[39] = nxt # the nxt is at the end of the pseudo header
|
||||
showAsHex(ipv6pseudoheader, "ipv6pseudoheader ")
|
||||
|
||||
udpHeader = bytearray(8)
|
||||
for i in range(0, 8):
|
||||
udpHeader[i] = ipv6frame[40+i] # in the real IPv6, we have also 40 byte IPv6 header, and afterwards the 8 byte UDP header
|
||||
showAsHex(udpHeader, "udpHeader ")
|
||||
|
||||
udpPayload = bytearray(udplen-8) # payload size is the announced udp size minus udpHeaderSize
|
||||
for i in range(0, len(udpPayload)):
|
||||
udpPayload[i] = ipv6frame[40+8+i]
|
||||
|
||||
showAsHex(udpPayload, "udpPayload ")
|
||||
|
||||
transmittedChecksum = udpHeader[6] * 256 + udpHeader[7]
|
||||
print("The transmitted checksum is " + hex(transmittedChecksum))
|
||||
|
||||
# Checksum algorithm:
|
||||
# 1. Set the checksum in the udp header to 00 00
|
||||
udpHeader[6] = 0
|
||||
udpHeader[7] = 0
|
||||
runningTotal = 0 # startvalue zero
|
||||
for i in range(0, len(ipv6pseudoheader)>>1):
|
||||
value16 = ipv6pseudoheader[2*i] * 256 + ipv6pseudoheader[2*i+1]
|
||||
runningTotal += value16
|
||||
if (runningTotal>=65536): # On each addition, if a carry-out (17th bit) is produced,
|
||||
runningTotal-=65536 # swing that 17th carry bit around
|
||||
runningTotal+=1 # and add it to the least significant bit of the running total.
|
||||
|
||||
for i in range(0, len(udpHeader)>>1):
|
||||
value16 = udpHeader[2*i] * 256 + udpHeader[2*i+1]
|
||||
runningTotal += value16
|
||||
if (runningTotal>=65536): # On each addition, if a carry-out (17th bit) is produced,
|
||||
runningTotal-=65536 # swing that 17th carry bit around
|
||||
runningTotal+=1 # and add it to the least significant bit of the running total.
|
||||
|
||||
for i in range(0, len(udpPayload)>>1):
|
||||
value16 = udpPayload[2*i] * 256 + udpPayload[2*i+1]
|
||||
runningTotal += value16
|
||||
if (runningTotal>=65536): # On each addition, if a carry-out (17th bit) is produced,
|
||||
runningTotal-=65536 # swing that 17th carry bit around
|
||||
runningTotal+=1 # and add it to the least significant bit of the running total.
|
||||
|
||||
# Finally, the sum is then one's complemented to yield the value of the UDP checksum field.
|
||||
checksum = runningTotal ^ 0xffff
|
||||
print("calculated checksum=" + hex(checksum))
|
||||
|
||||
# Same test, using the function
|
||||
myUdpFrame = bytearray(udplen) # payload size is the announced udp size
|
||||
for i in range(0, len(myUdpFrame)):
|
||||
myUdpFrame[i] = ipv6frame[40+i]
|
||||
|
||||
myIpv6Source = bytearray(16)
|
||||
myIpv6Dest = bytearray(16)
|
||||
for i in range(0, 16):
|
||||
myIpv6Source[i] = ipv6frame[8+i] # IPv6 source address
|
||||
myIpv6Dest[i] = ipv6frame[24+i] # IPv6 destination address
|
||||
|
||||
print("calculated with the function call: " + hex(calculateUdpChecksumForIPv6(myUdpFrame, myIpv6Source, myIpv6Dest)))
|
||||
Loading…
Reference in a new issue